The present invention relates to a novel mandrel lubricant and to a method for curing tubular elastomeric products such as flexible hose in which that lubricant is used.
It is known in the art to manufacture flexible hose, such as automotive radiator hose, by sliding a pre-cut length of uncured hose onto a pre-heated mandrel, which is often curved, and then heating and curing the hose. When the hose is cured, the hose substantially retains the mandrel's curved shape. One such method is described in U.S. Pat. No. 4,537,736.
In order to prevent the hose from adhering to the mandrel as it is cured and to enable a worker to remove the cured hose from the mandrel easily and to facilitate loading the hose onto the mandrel, it is common practice to apply a mandrel release agent to the inside of the uncured hose before the hose is slid onto the mandrel. A number of mandrel lubricants have been used for this purpose. Some of the most widely used are polyoxyalkylene based oils, pastes, waxes and greases. These lubricants are desirable because they are water soluble and they can be easily removed by washing with water. Polyoxyalkylene based lubricants are well known in the art. In addition to being described in U.S. Pat. No. 4,537,736, they are also disclosed in U.S. Pat. No. 4,217,394.
In spite of their wide use, polyoxyalkylene based lubricants have not been entirely satisfactory. To cure the hose, the hose is usually heated on the mandrel in an autoclave. At the elevated temperature and pressure of the autoclave and in the presence of steam, these lubricants become acidic due to oxidation of the mandrel lubricants, causing extensive corrosion to the mandrel and metal used in constructing the autoclave. Repair or replacement of the autoclaves with corrosion resistant materials such as stainless steel is expensive. Accordingly, there is a need for a less corrosive mandrel lubricant useful in the manufacture of flexible hose.